Electric sign



March 17, H Q MULBERGER V ELECTRIC SIGN Filed Aug. 28, 1959 I INVENTOR. flz/vev (T Must-case ATTORNEYS Patented Mar. 17, 1942 ELECTRIC SIGN Henry C. Mulberger, Waukesha County, Wis., assignorto AtomicResearch & Engineering Company, Milwaukee, Vis a corporation of Wisconsin Application August 28, 1939, Serial No. 292,278

2 Claims. (Cl. 40-130) This invention relates to electric signs and, more particularly, it relates to that type of electric sign employing gas filled and electrically energized tubes as the source of illumination.

The object of my invention is'to provide a reflected illumination having an intensity most nearly approaching the intensity of direct light produced by exposed electrically energized gas filled tubes.

In carrying out the purpose above stated, it is my object to provide a source of reflected light wherein the light source itself is one of the many types of electrically energized gas filled tubes, but the rays therefrom are reflected by a reflector having a characteristic such that the light rays of predominating frequency emitted by said tube are reflected with a high degree of efficiency by reflector surfaces which are matched spectroscopically with said predominating frequency, and rays of other than the predominating frequency are absorbed by the reflecting surface.

It is another object of my invention to provide for legible signs a reflected light which is more clearly legible for greater distances than the direct light from the well-known gaseous tube of the neon type.

Another object of my invention is to provide a sign or billboard generally shaped as a shallow box wherein a source of light comprising gas filled electrically energized tubes disposed in protected relation in the box supply light reflected by an interior surface of so called transparent paint identical in color with the color of the light emanating from such tubes, whereby substantially all of the supplied light is reflected and passed through the openings in the front of the box to delineate words comprising the legend portrayed by the sign.

It is a still further object of my invention to provide a sign of this general type which will have the intense visual characteristics of the type in which light emanates from exposed luminescent tubes, but at the same time the objectionable diffusion caused by side-band frequency interference which has heretofore reduced the legibility of signs of the exposed tube type will be absent by reason of said side-band frequencies being absorbed by the reflector surfaces, and hence even adjacent colors, such as green and red, may be read at extreme distances.

In the drawing:

Fig. 1 is a perspective view of an outdoor sign in which my invention is embodied; the front wall is shown partially removed to disclose the inner construction.

Fig. 2 is a front elevation in partial section of another embodiment of the invention showing the gaseous tubes leading into an energizing transformer.

Fig. 3 is a front view in partial section of a two-color sign showing a partition installed in the main box to prevent the colors from intermixing in the box.

Fig. 4 is a cross sectional View of the sign shown in Fig. 2 taken along line 4-4 of Fig. 2.

Like parts are identified by the same reference characters throughout the several views.

While I show specific embodiments of my invention in the signs illustrated in the drawing, it is understoodthat my principles are applicable to all forms of signs and reflected illuminations and I do not limit my invention to the specific types of signs shown. In this description, I have used the term spectroscopically similar and related expansions as referring to two surfaces having a light spectrum of approximately the same light frequency.

The outdoor type of sign shown in Fig. 1 includes a back surface 6, a front surface 1 which is-held in spaced relation to back 6 by means of supports along the edges In to form a shell or boxlike structure, a luminescent gas filled tube 9 which may be of the conventional neon filled type extending marginally about the inner edges of the box and a legend comprised of letters 8 which are cut through front 1 in stencil-like construction. Tube 9 has its ends terminating near an electrical energizing transformer which is not shown in Fig. 1, but may be mounted on the back of the sign or in any convenient location.

In my preferred embodiment of the invention, the inner wall of back 6 and front 1, as well as the inner walls of the separating supporting surfaces, are provided with a surface of so-called transparent or opaque paint or the like. These walls are rough. That is, they do not have a smooth surface such as glass, although most stock materials out of which signs are usually constructed, such as building board, pressed wood or planed lumber, have a sufficient roughness. The walls are first covered with a white surfacer, such as white lead and when this has dried, a transparent paint is applied.

To best understand what is meant by transparent paint and the proper test of such a paint as embodied in my invention, the following facts must be considered:

When a beam of white light is caused to pass through a piece of red glass, the red rays pass through the glass without obstruction whereas all the other components of the original beam are absorbed. This property is known as sheer selective absorption and it is possessed by many transparent materials but not by all such materials. If, for example, ground red glass is used as a pigment and is incorporated in a vehicle such as shellac which has relatively non-selective absorption properties, a paint is produced which may be called transparent because rays spectroscopically matched with the pigments will pass through the paint unobstructed and undeviated while rays of all other colors or frequencies will be absorbed by the pigments. The paint is, therefore, only transparent as to rays of a certain color frequency which, in this case, are red. If a film of this paint is applied over a very white surface, red rays will be reflected on the white surface as though no surface covered it while all other rays will be absorbed. These principles are advantageously incorporated in my sign in such a way that I effectively eliminate undesirable side band frequencies. 1

There is a definite correlation between the thickness of the transparent film and maximum reflection and the proper thickness must be experimentally determined in each case to compensate for the variable factor due to the consistency of the paint used. It is important to use as white an undercoat as possible. No white surface has a reflectance of 100% but several are obtainable with a. reflectance of approximately 90% While I prefer the above described method of reflecting the illuminating light rays, good results are also obtainable by the use of a nontransparent reflector film. Just as every colored light has a characteristic frequency which predominates, every colored reflective surface has a characteristic frequency with maximum reflectances obtainable by spectroscopically matching these fundamental frequencies and such resonance may be compared to the resonance between an electrical wave of a given frequency and a tuned circuit.

Fig. 2 represents an embodiment of my invention in which tube 90 terminates adjacent an electrical energizing transformer I2. I have found that excellent results are obtainable by placing the front and back walls of the sign relatively close together and, as this construction introduces a decided economy factor, I wish to designate it as my preferred method of construction. By way of example, in a sign having overall dimensions of 20 feet by feet, the inner box Walls or reflector surfaces need not be separated by more than 6 inches to get ample reflection.

Fig. 4 is a cross sectional view of the sign shown in Fig. 2 and illustrates the shallowness of my box type construction.

If it is desirable to use more than one color, the sign can be made up in sections as shown in Fig. 3 with a partition l6 separating the light from tube I09 from the different colored lights from tube 309. Separate transformers l3 and M are used in this case to energize respectively tubes I09 and 309, but the same transformer may be used to energize various tubes by merely increasing the electrical output of the transformer.

A shallow box of the type shown in the drawing is naturally less expensive than the deep boxes heretofore used for incandescent lights and I, also, accomplish a substantial saving by housing the neon tubes for my source of light within a box in protective relation not only to the weather, but in protected relation with respect to heedless or willful damage by marauders or vandals.

I claim:

1. A sign having a luminescent tube as a source of colored light and a reflective surface comprising substantially transparent protective material mixed with a pigmented material spectroscopically similar to the color of light from said source said protective and pigmented material being underlaid by a highly reflective surface.

2. A sign having a luminescent tube as a source of colored light and a reflective surface comprising substantially transparent protective material mixed with a pigmented material spectroscopically similar to the color of light from source, said protective and pigmented material being underlaid by a white surface.

HENRY C. MULBERGER. 

